Computed tomography (CT) is a good modality for diagnosing diseases of the retroperitoneal space and capable of showing the abnormality of inferior vena cava (IVC) without using invasive technique. To determine the incidence of the anomaly of IVC, the computed tomograms were investigated retrospectively. The incidence were 0.69% in left side IVC, 1.03% in double IVC and 0.08% in azygos continuation.